1. Field of Invention
The present invention relates to a kinetic state quantity estimating device and to a kinetic state quantity estimating method which are applied to a vehicle having a damper that generates a damping force corresponding to an orifice opening degree and designed to estimate a vertical kinetic state quantity of a sprung member relative to an unsprung member by means of an observer.
2. Description of Related Art
Relevant devices of this kind are disclosed, for example, in Japanese Patent Applications Laid-Open Nos. HEI 10-913 and HEI 9-309316. In these devices, a vertical acceleration of a sprung member is detected as a vertical kinetic state quantity thereof relative to absolute space. An observer estimates the relative speed of a sprung member by using the detected vertical acceleration as an input variable and a non-linear component of a damping force of a damper determined by an orifice opening degree as a control input. The estimated relative speed is indicative of a vertical kinetic state quantity of the sprung member relative to an unsprung member.
The aforementioned kinetic state quantity estimating devices according to the related art make it possible to precisely estimate a kinetic state quantity of the sprung member relative to the unsprung member at the time of heaving movements of the vehicle. However, a spring force of a stabilizer that influences movements of the sprung member and changes in road holding load resulting from roll and pitch movements of the sprung member are not taken into account in the devices of the related art. Therefore if the sprung member makes roll movements due to disturbance from a road surface, or if the sprung member makes roll movements when the vehicle turns, or if the sprung member makes pitch movements when the vehicle is accelerated or decelerated, the aforementioned relative kinetic state quantity cannot be estimated with high precision.